DRAM - University of California, San Diego

[Pages:32]DRAM

Dynamic Random Access Memory (DRAM)

? Storage ? Charge on a capacitor ? Decays over time (us-scale) ? This is the "dyanamic" part. ? About 6F2: 20x better than SRAM

? Reading ? Precharge ? Assert word line ? Sense output ? Refresh data

Only one bit line is read at a time. The other bit line serves as a reference. The bit cells attached to Wordline 1 are not shown.

Dynamic Random Access Memory (DRAM)

? Storage ? Charge on a capacitor ? Decays over time (us-scale) ? This is the "dyanamic" part. ? About 6F2: 20x better than SRAM

? Reading ? Precharge ? Assert word line ? Sense output ? Refresh data

Bitline 0 Wordline 0

Wordline 1

+

Bitline 1

Only one bit line is read at a time. The other bit line serves as a reference. The bit cells attached to Wordline 1 are not shown.

Dynamic Random Access Memory (DRAM)

? Storage ? Charge on a capacitor ? Decays over time (us-scale) ? This is the "dyanamic" part. ? About 6F2: 20x better than SRAM

? Reading ? Precharge ? Assert word line ? Sense output ? Refresh data

Bitline 0 Wordline 0

Wordline 1

+

Bitline 1

Only one bit line is read at a time. The other bit line serves as a reference. The bit cells attached to Wordline 1 are not shown.

Dynamic Random Access Memory (DRAM)

? Storage ? Charge on a capacitor ? Decays over time (us-scale) ? This is the "dyanamic" part. ? About 6F2: 20x better than SRAM

? Reading ? Precharge ? Assert word line ? Sense output ? Refresh data

Bitline 0 Wordline 0

Wordline 1

+

Bitline 1

Only one bit line is read at a time. The other bit line serves as a reference. The bit cells attached to Wordline 1 are not shown.

Dynamic Random Access Memory (DRAM)

? Storage ? Charge on a capacitor ? Decays over time (us-scale) ? This is the "dyanamic" part. ? About 6F2: 20x better than SRAM

? Reading ? Precharge ? Assert word line ? Sense output ? Refresh data

Bitline 0

Bitline 1

Wordline 0

Bit destroyed!

Wordline 1

+

Only one bit line is read at a time. The other bit line serves as a reference. The bit cells attached to Wordline 1 are not shown.

Dynamic Random Access Memory (DRAM)

? Storage ? Charge on a capacitor ? Decays over time (us-scale) ? This is the "dyanamic" part. ? About 6F2: 20x better than SRAM

? Reading ? Precharge ? Assert word line ? Sense output ? Refresh data

Bitline 0 Wordline 0

Wordline 1

+

Bitline 1

Only one bit line is read at a time. The other bit line serves as a reference. The bit cells attached to Wordline 1 are not shown.

Dynamic Random Access Memory (DRAM)

? Storage ? Charge on a capacitor ? Decays over time (us-scale) ? This is the "dyanamic" part. ? About 6F2: 20x better than SRAM

? Reading ? Precharge ? Assert word line ? Sense output ? Refresh data

Bitline 0

Bitline 1

Wordline 0

Bit Restored

Wordline 1

+

Only one bit line is read at a time. The other bit line serves as a reference. The bit cells attached to Wordline 1 are not shown.

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